Heating of fluids



Feb. 7, 1939. M w BARNES l2,146,497

HEATING OF FLUIDS Filed July 25, 1935` MARI L&%Q@@f%%% gg@ wb @SNQ INVENTOR u ON W. BARNES ATTORNEY y l this is desirable with 4 80 section due to the fact Patented Feb. 7, 1939 UNITED STATES PATENT OFFICE nEA'rmG oF FLUms Marion W. Barnes, Chicago,

Ill., assignor to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application VJuly 26, 1935, ySerial No. 33,207

3 Claims.

` rates of heating in different portions of uid conduits through which hydrocarbon oils pass in a continuous stream and are therein heated to the high temperatures required for their pyrolytic conversion is now well established. While practically all types of oils it is particularly essentialwhen cracking or reforming oils of relatively low-boiling characteristics such as gasoline, naphtha, kerosene or kerosene distillate and the like, wherein, according tothe best present practice, the oil is quickly heated to the desired relatively high conversion temperature and then maintained for a predetermined time at a substantially uniform temperature near the maximum previously attained.

26 In such operations the last portion of the heating coil or uid conduit wherein the oil is maintained at ahsubstantially constant temperature is termed a soaking section". Relatively low rates of heat input are ordinarily required in the soaking that only a portion of the latent heat of -cracking and vaporization4 and only a relatively small or no appreciable amount 'of sensible heat is absorbed by the oil in this zone.

The features of the present invention are particularly desirable in light oil cracking or reforming operations since they permit relatively low rates of heating about the flnal or soaking section of the fluid conduit with independently 40 controlled higher rates of heating in the preceding portion of the nuid conduit. wherein the oil may be rapidly heated'to the desired relatively high conversion temperature and, in addition, permit preheating of the charging stock supplied to the fluid conduit to a temperature below that at which any appreciable conversion thereof will occur in the rst portion of the fluid conduit which is supplied with convection heat from the hot combustion gases from both of the preceding heating zones of the furnace prior to their removal from the furnace. In the present invention this is accomplished in a simple and inexpensive form of furnace and without sacrificing furnace emciency. In one embodiment. the apparatus of the present invention comprises a furnace having side walls, end walls, a roof and a floor, a centrally located horizontal wall extending between the side Walls of the furnace from one end wall to' nea-r the opposite end wall and dividing the furnace into an upper and a lower combustion and heating zone, means for supplying controlled amounts of combustible fuel and air to the lower combustion and heating zone, means for passing combustion gases from said lower zone into and through the upper combustion and heating zone, means for independently supplying controlled amounts of combustible fuel or air or both to the upper combustion and heating zone in commingled state with the combustion gasesfromsaid lower zone, fluid conduits located within the lower combustion and heating zone and subjected to heating primarily by radiation from the materials undergoing combustion and the hot refractory walls of this zone, uid conduits located Within the upper combustion and heating zone and subjected to heating primarily by radiation from the materials undergoing combustion in this zone of the furnace and the hot refractory walls thereof, another uid conduit located within said upper zone and subjected to heating by .contact with the combustion gases therein and means for removing combustion upper zone.

As employed in the conversion or reforming of low-boiling hydrocarbon oil the ow of oil through the fluid conduit may be, for example, ilrst through the fluid conduit in the upper zone of the furnace which is subjectedv to heating by contact with the combustion gases, thence through the fluid conduits in the lower combustion and heating zone and nally through the fluid conduits in the upper combustion and heating` zone which are subjectedv toV heating primarily by radiation; the last mentioned portion of the heating coil serving as a soaking section.

The accompanying diagrammatic drawing il- .Y lustrates one specic form of furnace embodying the features and advantagesv of the present invention and the process of the invention will be more apparent with reference to the following description |of the drawing.

Referring to the drawing, which is a longitudin al elevation of the furnace in cross-section, the main furnace structure comprises end walls I and 2, a roof 3, a oor 4 and side walls which are no'` indicated in the particular view of the furnace illustrated. A centrally located horizontal'wall 5 extending between the side walls oi' the furnace from en d wall l to near the opposite gases from said themain stream of flow tofy end wall 2 divides the interior of the furnace into lower combustion and heating zone 6 and upper combustion and heating zone 1, serving as the roof of the lower zone and the oor of the upper zone. A space is provided between end wall 2 and the adjacent end of wall 5 permitting the passage of combustion gases from zone 6 into zone 1.

Combustible fuel and air may be supplied to combustion and heating coil 5 through one or preferably a plurality of suitable firing tunnels such as indicated, for example, at 8. Any desired type of fuel such as oil, gas or pulverized solid fuel is supplied, together with air or steam for atomization thereof, through a suitable burner 9 to the central portion comprising firing compartment I of the tunnel. Regulated amounts of additional air may be supplied to compartment IIJ by means of a suitable damper II and any additional air required for combustion as well as any desired amount of auxiliary air may be supplied to the combustion and heating zone through air ducts I2 controlled by dampers I3 and located above and beneath compartment I0. The relative proportions of the total combustion taking place in tunnels I0 and combustion and heating zone Ii as well as the length of the ame issuing from the combustion compartments of the firing tunnels may be controlled by regulating the relative amounts of total air supplied to this zone through compartments I0 and I2 respectively and the total amount of air supplied to combustion and heating zone 6 relative to the fuel supplied thereto will determine the completeness of combustion of the fuel in this zone. One or a plurality of similar firing tunnels indicated at 8' communicate through end wall 2 of the furnace with combustion and heating zone 1. Burner 9', firing compartment I0', damper II', air ducts I2 and dampers I3' of tunnel 8 function in the same way as the similar parts of firing tunnel 8 so that controlled additional amounts of combustible fuel air or both may be commingled in combustion and heatingzone 1 with the combustion gases from combustion and heating zone 8 in order to provide additional heating in the upper combustion and heating Zone,las required, so that independentlycontrolled heating conditions may be maintained in the upper and lower combustion and, heating zones of the furnace.

It is ofcourse within the scope of theinvention to employ conventional burner ports. or any other well known iiring arrangement forlsupplying combustible fuel to either combustion heating zone 6 or combustion heating zone 1, or both, in place of the firing tunnels 8 and 8' illustrated in the drawing. f

Fluid conduits I4 comprising, in the particular case here illustrated, .a single horizontahrow of horizontally disposed tubes is located immediately beneath wall 5 in combustion, and heating zone E. A similar fluid conduit I5 is located adjacent the floor of the furnace. ofcombusrtion and heating zone 6. These conduits are-heated primarily byradiation from the materials undergoing combustion in zone 8 of the furnace and the adjacent hot refractory furnace walls and a protrusion I6 fronrthe lower. side. 'of'. wall serves to minimize washing ofthe tubes of fluid conduit I4 by thecombustion gasesby directing lthese productsrtoward the central lportion .of this zone. AA fiuid Vconduit I 1 comprising, in the. particularlcase. `here .illustrated, two horizontal parallel rows of horizontally disposed tubes arranged. in staggered :for-

mation is located immediately above wall 5 in combustion and heating zone 1. A similar uid. conduit I8 is located adjacent roof 3 of the furnace in zone 1. Fluid conduits I1 and I8 are heated predominantly by radiation from the materials undergoing combustion in zone 1 of the furnace and the adjacent hot refractory furnace walls. Protrusions I9 and 28 from walls 5 and 3, respectively, serve to direct the main stream of ow of the combustion products through the central portion of zone 1 in order to minimize washing of the tubes of fluid conduits I1 and I8 by the hot combustion gases.

In the case here illustrated, the end of the upper combustion and heating zone 1 adjacent end wall I of the furnace comprises convection heating zone 2I in which is located another uid conduit 22 comprising, in the case here illustrated, a plurality of parallel rows of horizontally disposed tubes which are heated by contact with the combustion gases from the preceding portion of zone 1. The two or three rows of tubes of con'- duit 22 adjacent that portion of zone 1 containing fluid conduits I1 and I8 are, of course, also subjected to an appreciable amount of heating by radiation from the materials undergoing combustion in this zone but combustion is preferably so controlled in the upper combustion and heating zone 1 that it is substantially completed before the gases reach fluid conduit 22. The combustion gases, after passing over the tubes of fluid conduit 22, are directed from the furnace through flue 23 controlled by damper 24 to a suitable stack, not illustrated.

In the particular case here illustrated the fluid undergoing heating flows in series through the various conduits 22, I4, I5, I1 and I8 in the order mentioned and the various tubes of each of these conduits are connected in series, in the manner indicated by the single lines connecting adjacent tubes. Line 25 and the dotted lines 26, 21 and 28 indicate crossover connections between the various tube banks located outside of the furnace.

It will be understood, of course, that the invention is not limited to the specific form of furnace illustrated and above described nor to theV specific arrangement of fluid conduits or flow of fluid therethrough which is illustrated in thedrawing since many modifications thereof maybe made without departing from the broad features and advantages of the invention.

lAs a specific example of operating conditions which may be obtained in a furnace of the character illustrated and above described as employed for. the reforming of straight-run gasoline, for example, the oil which is supplied-to fluid conduit 2 2 at 4substantially `atmospheric temperature lis heated-V therein to a 'temperlature of ap- .,proximately F. and is thence passed through fluid conduits I4 and -I5 wherein theternperature yis increasedto approximatelydto 975 F. and

is finally passed through fluidconduits I1 and I8 wherein itremains. for a sufficient length of time to complete thedesiredconversion at a tempera- ,tureof .approximately 1000 to 1035" F., a superatmospheric.pressure of about 800 pounds per square inch being maintained atV the outlet from Ythe soaking section and the oil .being discharged -rtherefrom to subsequentportions ofthe cracking system` not pertinent to An average. temperaturev of approximately, 1600 -F.is .maintained .adjacent fluid .conduits I4 -and I5.lncombustion and heating (zone, Ii.. The gases leave zone 6 at a temperature of .approximately r`.1.4.0.0".-l.;which incrased to approximately the present invention..

1500 1". as they enter zone 1. 'I'he average temperature `adjacent uid conduits i1 and I8 in combustion and heating zone 1 is approximately 1350 F. The combustion gases enter the connection heating section of the furnace containing conduit 22 at a temperature of approximately 1200 F. and the ue gas temperature from the furnace is approximately 450 F. The overall thermal emciency of the furnace in this operation is approximately 65 to 70 per cent.

I claim as my invention:

1. A fluid heating apparatus comprising a furnace having a oor and a roof, a horizontal wall spaced from the iioor and roof and dividing the furnace into a lower heating section and an upper heating section. means for passing combustion gases from one of said' sections through the other section, heating tubes adjacent said floor, heating tubes adjacent said roof, additional heating tubes in said lower section adjacent the underside of said wall, additional heating tubes in said upper section adjacent the upper side of said wall and means for independently ring each of said sections in a generally horizontal direction between the upper and lower' tubes contained therein, said-.tubes being disposed out of the main path of combustion gases through the furnace.

2. A duid heating apparatus comprising a furnace having a iioor and a root, a horizontal wall spaced from the iloor and root Aand dividing the furnace into a lower heating section and an upper heating section, means for passing combustion gases from one oi' said sections through the u other section, heating-tubes adjacent said'iloor,4

heating tubes adjacent said roof, additional heating tubes in said lower section adjacent anais? 3 the underside oi.' said wall, additional heating tubes in said upper section adjacent the upper side of said wall and means for independently ring each of said sections in a generally hori-A zontal direction between the upperl and lower tubes contained therein, said tubes being disposed out of the main path of combustion gases through the furnace-whereby they are heated predominantly by radiation, means for removing combustion gases from the section receiving combustion gases from the other secti0n,'and

convection heating tubes disposed in the path of the combustion gases discharging from said section receiving combustion gases from the other section.

3. A uid heating apparatus comprising a fur-` nace having a iioor and a roof, a horizontal wall spaced from the oor and roof and dividing the furnace into a lower heating section and an up# per heating section, means for passing combustion gases from one of said sections through the other section, heating tubes adjacent said door, heating tubes adjacent said roof, additional heating tubes in said lower section adjacent the underside of said wall, additional heating. tubes in said upper section adjacent the uppei side of said wall and means for independently iiring each of said sections in a generallyl horizontal' direction `between the upper and lower tubes contained therein, said tubes being out of the main path of combustion vgases through the'iurnace whereby they areheated predominantly by radiation, and convection heating tubes disposed in the path of thecombustion gases through the section receiving combustion gases from the other section. MARION W. BARNB. 

